Cast corrosion inhibitor particle for oil wells



United States CAST CORROSION INHIBITOR PARTICLE OIL WELLS Everett N. Case, Homewood, 111., assignor to Sinclair Refining Company, New York, N.Y., a corporation of Marne N Drawing. Application July 22, 1957 Serial No. 673,109

6 Claims. (Cl. 252-855) This invention relates to corrosion inhibitor for use in inhibiting the corrosion of metal tubing and casing in oilwells. More particularly, this invention relates to a corrosion inhibitor composition for inhibiting the corrosion of metal parts actually submerged in a brine layer at the bottom of an oil well.

Among the etiective and highly desirable corrosion inhibitors are ones which are oil-dispersible and waterdispersible. The term dispersible is used to indicate that the inhibitor is soluble, miscible or otherwise dispersible in the medium mentioned without continuing agitation. In general practice these inhibitors are employed as solutions in oil or as an inhibitor composition cast into solid sticks. As a solution in oil, the inhibitor is forced down the well tubing or poured down the well inside the casing, and in cases Where the inhibitor composition is a solid stick, it is dropped through the well tubing or the space between tubing and the well casing. These inhibitors are intended to protect primarily the metal which contacts the oil portion of the liquid of a well.

However, in addition to the corrosion which takes place on metal parts contacting the oil, there is arserious corrosion problem in some Wells where part of the casing and tubing are actually submerged in a brine layer atthe. bottom of the well beneath the oil.layer. Obviously, the introduction of an oil-dispersible inhibitor with water-dispersible properties does little good in this case for it has been found that only a small portion, if any, of the inhibitor reaches the brine layer. As a consequence of its dispersibility properties, the major portion of the inhibitor, whether it be employed as a solution in oil or as a solid, goes into solution as it. passes through the oil layer to reach the brine layer. It has been suggested that the introduction of large pieces of solid inhibitor would remedy the problem since the presumed rate of travel through the oil layer would be high enough to make the loss of material by solution negligible. However, the utilization of inhibitor solids of large particle size has experienced considerable ,difficulty since the irregular annulus in a well between the tubing and casing lessens considerably the chance of the inhibitor reaching the lower portion of the well hole Within a reasonable and determinable time.

In the present invention I prepare a novel composition of matter which when introduced into a well, e.g. in the annulus between the casing and tubing, will reach the brine layer at the bottom of the well and therein effectively inhibit the corrosion of metals, particularly ferrous metals, submerged in the brine layer. '1 am aware that corrosion inhibiting pellets have been proposed for multiphase liquid systems, e.g. see US. Patent No. 2,795,560; however my invention is designed to overcome problems presented when employing the highly useful class of corrosion inhibitors which remain dispersed in both oil and waterwithout continuing agitation. In accordance with my invention, I have dis- Covered a corrosion inhibitor mixture, formed into a invention must act as a protective carrier for the actual oil-dispersible corrosion inhibitor as it passes through the oil layer to reach the brine layer. The watersoluble carrier should have a low melting point so that the corrosion inhibitor is not destroyed when making the composition at elevated temperatures by melting the carrier. Since the major component of the solid composition will frequently be the water-soluble carrier material, especially if the corrosion inhibitor is a liquid or sticky material, the cost of the carrier can be an important factor. It has been found that oil-insoluble, water-soluble carrier materials selected from the group consisting of urea and hydrated sodium acetate have the desired properties. When these materials are compounded with an oil-dispersible, water-dispersible corrosion inhibitor component, Weighted by the addition of suitable weighting agents, and introduced into a Well containing oil, the composition is designed to effectively inhibit the corrosion of well tubing and easing submerged in the brine layer at the bottom of the well.

As the corrosion inhibitor component of my invention, many of the conventional materials 'widely known in the prior art as corrosion inhibitors may be employed. The corrosion inhibitor component is oil-dispersible and water-dispersible. When necessary or desirable the water-dispersibility of the inhibitor can be provided by the use of emulsifying or dispersing agents as part of the corrosion inhibiting composition. Among the corrosion inhibitors that can be employed are: the primary, secondary and tertiary amines from octyl to octadecyl, such as n-octadecylamine, di-n-dodecylamine, and cyclohexylamine; ammonium compounds or amine salts formed by reacting an aliphatic, naphthenic or aromatic amine with a fatty acid, e.g. cyclohexylammoni-um xylyl stearate, decyclohexylammonium xylyl stearate, tetramethylamrnonium stearate, octadecylammonium oleate, dicycloammonium oleate, oleylammonium oleate; esters such as the lower aliphatic esters of 12-hydroxystearic acid, the glycol esters; alpha-monopalmatin, glycerol monoand dioleate, sorbitan mono and trioleate; soaps or salts or carboxylic acids, e.g. zinc 4-ethyl octanoate, zinc laurate, zinc stearate, zinc dodecylphenyl stearate, zinc xenyl stearate, zinc dibenzyl acetate, zinc naphthenate, magnesium stearate, magnesium Xylyl stearate, magnesium naphthenate, barium phenyl stearate, calcium Xenyl stearate, calcium oleate, calcium naphthenate, aluminum monostearate, aluminum naphthenate, lead oleate, lead ricinoleate, lead naphthenate; amine salts of carboxylic acids, e.g. octadecyl, secondary octadecyl, heptadecyl, dodecyl, decyl and octadecyl amine salts of ricinoleic, lauric, caprylic, stearic, palmitic and oleic acids. Of course, other suitable inhibitors are known and these are also useful.

The preferred corrosion inhibitors of this invention, however, are the aromatic sulfonate type of inhibitors. By aromatic sulfonate type of inhibitors, I mean those inhibitors depending at least in part on a sulfonate content for corrosion inhibiting activity. Suitable inhibitors of this type include, for example: oil-dispersible,

neutralized hydrocarbon-insoluble petroleum sulphonic acids, sometimes known as green acids, such as the salts of hydrocarbon-insoluble petroleum sulfonic acids and at least one aliphatic amine having from 12 to 30 carbon atoms per molecule. 'These hydrocarbominsoluble sulfonic acids are identified as those which are present in the acid layer rather than the hydrocarbon layer when pet-r9- leum fractions generally within the kerosene to lubricating oil range are sulfonated with either S ,or strong or fuming H 504 in accordance with procedures well-known in the art. Among the aliphatic amines which may be used in providing these neutralized aromatic sulfonate salts are dioctyl amine, didecyl amine, didodecyl amine, tetradecyl amine, hexadecyl amine, octadecylamine, N- methyltetradecyl amine, N-butyltetradecyl amine, N,N- dimethyldocosyl amine, N,N-diethyldodecyl amine, N,N- dimethyldocosyl amine, N,N-diethyldode cyl amine, methyl didodecyl, N-ethyloctadecyl amine and methyldihexyl amine.

Of this group of corrosion inhibitors, particularly preferred are the salts of hydrocarbon-insoluble petroleum sulphonic acids and Duomeen T, a fatty amine having both primary and secondary amine groups. It has the structural formula:

wherein the R group consists of straight chain hydrocar- -bon radicals derived from tallow acids which are 16 and 18 carbon atoms in length. Duomeen T is commercially produced by Armour and Company.

Others of the aromatic sulfonates are:

The ammonia-neutralized sulfonated Neolene bottoms. This product is prepared by the sulfonation and subsequent neutralization with ammonia of the bottoms produced in the manufacture of monodecylbenzene; i.e. the bottoms remaining after fractionation to remove the monodecylbenzene from the reaction products of dodecene With benzene, which bottoms consist essentially of di-dodecylbenzene along with polyalkylated benzene molecules. Neutralized hydrocarbon-soluble petroleum sulfonic acids, commonly known as mahogany acids, such as alkali and alkaline earth metal and ammonium mahogany sulfonates. The mahogany acids are those present in the hydrocarbon layer rather than the acid layer when petroleum fractions generally within the kerosene to lubricating oil range are sulfonated with either S0 or strong or fuming sulfuric acid in accordance with procedures well-known in the art.

It is to-be understood that whenever the corrosion in hibitor employed is not sufficiently water-.dispersible good dispersing or emulsifying agents should be utilized. Examples of suitable dispersing and emulsifying agents for use in my invention are the emulsifying agents known commercially as Brij, Span 80, Tween 85, Triton X45 and Triton X-lOO.

Brij is the series of polyoxyethylene fatty alcohol derivatives commercially produced by Atlas Powder Company. An example is oxyethylated lauryl alcohol.

Span 80 is commercially available (Atlas Powder Company) and is comprised of long chain fatty acid partial esters of hexitol anhydrides. It is an oily liquid having a flash point of about 410 F., a fire point of about 545 F. and a specific gravity of about 1.00 to 1.05. The long chain fatty acids which are employed in producing the fatty acid partial esters of hexitol anhydride contain about 12 to 24 carbon atoms per molecule. The. acids can be saturated or unsaturated and include, for example, lauric, palmitic, stearic and oleic acids. By hexitol anhydride is meant inner ethers having one cyclic oxygen per ring derivable from a hexahydric alcohol by intermolecular condensation and includes the mono-anhydric and dianhydro derivatives, i.e. hexides, hexitans, mannides, manitans and the like. By partial ester is meant that the hydroxy group of the anhydride are not all esterified; mono-, diand triesters and mixtures thereof are preferred and these can be simple or mixed esters.

Tween 85 is the reaction product of about 5 mols of ethylene oxide and one mol of sorbitan trioleate, and is a product of the Atlas Powder Company. It is an oily liquid at 25 C. having a flash point of about 565 F., a fire point of about 645 F. and specific gravity of about 1.00 to 1.05.

Span and Tween are both disclosed in US. Patent No. 2,695,877 to Nichols.

Triton X45 and Triton X- are polyether alcohols available commercially from the Rohm & Haas Company. They comprise alkyllauryl polyether alcohols having the general formula R(O-CH -CH ),,-OH Where R is an alkylaryl radical and n is an integer from about 5 to 100 or more, preferably 5 to 25. The Tritons are the preferred polyether alcohols and are liquid mixtures of homologous polyether alcohols. Triton X-45 is readily miscible with formalin and the common organic solvents. Triton X-100 is essentially identical with Triton X-45, differing primarily in the average length of the polyether chains. Triton X-100 is water-soluble at room temperature, is miscible with alcohol and compatible with esters, ketones and aromatic hydrocarbons.

The weighting agents of the present invention are employed to give the carrier-corrosion inhibitor mixture a density greater than that of oil. It is important that the weighting agent employed be inert as far as the other ingredients are concerned and preferably water-soluble or water-dispersible to permit their removal from the well. Examples of suitable weighting agents are barium sulfate, barium carbonate, barium oxide, iron oxide, lead oxide and iron metal. The weighting agent itself should generally have a minimum density of greater than 3, preferably at least 4, and the density can be up to 8 or 10 or more and should be added in an amount sufficient to give the final corrosion inhibitor mixture a density greater than that of oil, e.g. a density of at-least about 2. The amount of weighting agent added is generally a quantity constituting about 2 to 10 parts by weight of the final corrosion mixture.

To prepare the solid corrosion inhibitor mixture of this invention the oil-insoluble, waltezr-eoluble carrier component is melted and thoroughly mixed with the corrosion inhibitor. Prior to the mixing, a dispersing agent such as oxyethylated lauryl alcohol is added to the corrosion inhibitor if the corrosion inhibitor employed is not by itselfsufiiciently water-dispersible. The addition of 0.5 to 2.0% of dispersing agent based on the corrosion inhibitor employed is sufficient to disperse the corrosion inhibitor when it reaches the'bottom of the well. Since most water-dispersible corrosion inhibitors are liquids or sticky masses, a weight ratio of carrier component to corrosion inhibitor of at least about 1:1 is preferred so as to obtain a solid. Thus the carrier is frequently the major component of the'composition, preferably 8 to 16 parts by Weight, while the inhibitor is the minor component. There mightbe as little as about 2 parts by weight of the carrier present, but if the corrosion'inhibitor is a liquid a much higher ratio than 1:1 of carrier component to inhibitor may be needed. Sufficient inhibitor must be present to provide the desired corrosion inhibitor, e.g. about 1 to 11 parts by weight of the mix, preferably about 1 to 5 parts. A weighting agent such as barium sulfate is then added in quantity sufficient to give the corrosion inhibitor mixture a density of at least about 2. If desired, to the inhibitor mix may be added a Water-soluble material such as alum to lower the melting point of the mix, a bactericide for bacteria control in the Well hole or other desirable components. After thorough mixing, the product is poured onto a flaking machine where it is cooled to provide an intimate bond between the carrier and inhibitor, chipped off and screenedto obtain the particle size desired. Generally Percent by volume Water-soluble petroleum green sulfonio acids 19.6. DuomeenT 12.8. Isopropanol 21.8. Solvent 1 45.8. NH 4.4#/ 100 gal. of final inhibitor solution. A highly aromatic solvent such as benzene or xylene.

Preparation of the above corrosion inhibitor is carried out as follows:

The solvent is added to a mixing kettle and the watersoluble sulfonic acids (water-soluble green acids having a molecular weight of about 325) added with thorough mixing. Approximately one-fifth of the alcohol is added to aid in solubilizing the mixture. A small amount of anhydrous ammonia also is added for the same purpose. Next the Duomeen T is added slowly resulting in essentially complete neutralization of the water-soluble sulfonic acids. NH is again added to a total of roughly 4.4 pounds per 100 gallons of final inhibitor. Three percent of water is now added and the inhibitor heated to 150 to 155 F. and the remainder of the alcohol added. The mass is allowed to set without agitation for a period of 8 to 12 hours at 130 to 140 F. Any clear brine which separates is drawn from the kettle. The solvent which was added to facilitate the preparation is removed as completely as possible. The heavy viscous residue is the final corrosion inhibitor component.

Approximately 2 parts by weight of the above corrosion inhibitor composition is mixed with about 1.0 percent of its weight of oxyethylated lauryl alcohol (Brij). The mixture forms a very heavy liquid which is then mixed with approximately 8 parts of melted urea containing about of its weight of alum to lower the melting point of urea. Approximately 4 parts of barium sulfate weighting agent is then added. After thorough mixing, the product is poured onto a flaking machine where it is cooled to solidify and then chipped off. The chips of product are then screened to obtain the particle sizes desired, e.g. between about to 2 inches and the undesired and oversized particles remelted. The product so produced is substantially oil-insoluble, has a density of approximately 2.0 (thus is heavier than oil) and dissociates in water to give a milky solution.

6 The milky appearance is indicative of the dispersion of the inhibitor in the water.

Example II Two parts of the inhibitor-dispersing agent mixture of Example I is mixed with 14 parts of melted hydrated sodium acetate. Approximately 4 parts of barium sulfate as a weighting agent is then added. This mixture is not a solution but a dispersion and when cooled with agitation produces lumps which are an intimate mixture of the corrosion inhibitor and carrier components. The lumps so produced are then broken up and are screened to obtain particle sizes between inch and 2 inches. The resulting product is substantially oil-insoluble and has a density greater than that of oil.

I claim:

1. A cast corrosion inhibitor particle having a density greater than that of oil and consisting essentially of about 2 to 16 parts by weight of an oil-insoluble, watersoluble carrier component, selected from the group consisting of urea and hydrated sodium acetate, about 1 to 11 parts by weight of an oil-dispersible, water-dispersible corrosion inhibitor, and a suificient amount of a weighting agent having a density greater than about 3 to provide the particle with a density greater than that of oil.

2. The composition of claim 1 in which the carrier is urea.

3. The composition of claim 1 in which the carrier is hydrated sodium acetate.

4. The composition of claim 1 in which the weighting agent is barium sulfate.

5. The corrosion inhibitor mixture of claim 1 in which the corrosion inhibitor is a water-soluble petroleum sulfonic acid neutralized with wherein the R group is a straight chain hydrocarbon radical derived from tallow acids.

6. In a method of protecting ferrous metal well equipment from corrosion due to water in a well having a water layer in its lower portion and below an overlying oil layer, the step comprising adding to the oil layer the corrosion inhibitor of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,583,399 Wachter et al Jan. 22, 1952 2,684,332 Rohrback et a1 July 20, 1954 2,698,295 Caldwell et al Dec. 28, 1954 2,756,211 Jones July 24, 1956 2,795,560 Williams June 11, 1957 

1. A CAST CORROSION INHIBITOR PARTICLE HAVING A DENSITY GREATER THAN THAT OF OIL AND CONSISTING ESSENTIALLY OF ABOUT 2 TO 16 PARTS BY WEIGHT OF AN OIL-INSOLUBLE, WATERSOLUBLE CARRIER COMPONENT, SELECTED FROM THE GROUP CONSITING OF UREA AND HYDRATED SODIUM ACETATE, ABOUT 1 TO 11 PARTS BY WEIGHT OF AN OIL-DISPERSIBLE, WATER-DISPERSIBLE CORROSION INHIBITOR, AND SUFFICIENT AMOUNT OF WEIGHTING AGENT HAVING A DENSITY GREATER THAN ABOUT 3 TO PROVIDE THE PARTICLE WITH A DENSITY GREATER THAN THAT OF OIL. 